The present invention relates to a valve operating apparatus for an internal combustion engine. More particularly, the invention involves a valve operating apparatus in which the intake or exhaust valves are operated by pivotally mounted, cam-driven rocker arms having a selective coupling operative between the rocker arms to open and close the valves in response to a camshaft rotated in synchronism with the operation of the engine.
Valve operating apparatus of the described type are disclosed, for example, in U.S. Pat. No. 4,545,342, granted Oct. 8, 1985 to Y. Nakano et al.,and assigned to the assignee herein. In such valve operating apparatus the cam follower is held in direct sliding contact with the rotating cam. Where the cam follower is in direct sliding contact with the cam, however, friction losses in the system are significantly great, as is the amount of wear in the respective cam and cam follower surfaces.
There has been proposed, as disclosed in Japanese Laid-Open Patent Publication No. 61-19912, a device in which a rotating body held in sliding contact with a cam is rotatably supported on a piston of a selective coupling. While such a rotating body can be disposed in a certain rocker arm according to this prior art, however, it would be difficult in a layout to provide rotating bodies in all rocker arms since the pistons are moved.
It is to the amelioration of this problem that the present invention is directed.